1. Field of the Invention
The present invention relates to a method for manufacturing a piezoelectric device that includes a piezoelectric single crystal thin film.
2. Description of the Related Art
Many piezoelectric devices obtained by thinning a piezoelectric single crystal body have been developed. In such a piezoelectric device, an electric field for polarization is applied to stabilize the polarization of the piezoelectric single crystal body that defines a piezoelectric thin film. For example, for a piezoelectric device disclosed in Japanese Unexamined Patent Application Publication No. 5-90859, a pair of metal films are formed on the front and back surfaces of a flat piezoelectric base material, and an electric field for polarization is applied using the pair of metal films as opposed electrodes. For a piezoelectric device disclosed in Japanese Unexamined Patent Application Publication No. 2007-43054, a lower electrode utilized to drive the piezoelectric device is used as an electrode for applying an electric field for polarization.
However, in the manufacturing method described in Japanese Unexamined Patent Application Publication No. 5-90859, an electric field is applied to the entire piezoelectric base material. Therefore, an electric field has to be applied to the composite substrate including the piezoelectric thin film and the supporting substrate, despite the fact that an electric field only needs to be applied to a piezoelectric thin film in a structure in which the piezoelectric thin film is supported by a supporting substrate. This requires the application of extremely high voltage. Consequently, breakage of a substrate occurs due to abnormal electric discharge or large-scale equipment for ensuring safety when performing high electric field application needs to be installed.
In the manufacturing method described in Japanese Unexamined Patent Application Publication No. 2007-43054, since a lower electrode of a piezoelectric device is used as an electrode for applying an electric field for polarization, an electric field for polarization cannot be applied to a piezoelectric device having no lower electrode.